Such devices are typically used to continuously maintain tension on the chain or the belt in a specific range of tension value or to locally modify the path taken by the chain or belt. This is called tensioner or idler, respectively. In idlers, the pulley is rotatably mounted on a screw or an axle via a bearing, the idler being fixed directly or indirectly to an engine block or to an element of an idler assembly, such as an arm or an eccentric. The bearing is a mechanical device for implementing the pivot connection between the pulley and the screw or axle, and may be a rolling bearing for this purpose.
A spacer cooperating with the screw or axle is typically used to fix the idler on its support. It is desirable during the idler mounting that the screw or the axle is axially secured to the other elements of the idler and including the pulley. This provides a non-removable assembly which is easy to handle and transport, and be easily mounted.
For this purpose, it is known from EP-A1-1 120 584 a device providing a pulley, a bearing, a spacer supporting the bearing and a fastening screw axially immobilized relative to the spacer. An elastic ring allows the axial retention of the screw relative to the spacer. However, this solution has the drawback that the elastic ring is difficult to install and its position is not always maintained.
In FR-A1-2 954 437, another axial retaining means for the screw is described, including a retainer ring interposed between the spacer and the fastening screw and able to cooperate with a specific groove provided to the screw. This solution is not fully satisfactory since it requires a special design of the screw. Moreover, there is a risk of loss of the retainer ring before mounting of the fastening screw when assembling the device. A relatively large clearance has to be provided to the front surface of the spacer to allow the retainer ring mounting. It reduces the contact surface between the spacer and its support.
The present invention aims to remedy these drawbacks.